BIOMECHANICAL CHARACTERISTICS OF LOW BACK TISSUES DURING TRUNK FLEXION-EXTENSION
- 몸통 굴곡신전 동안 허리조직의 생체역학적 특성
시간있다면 꼭 한번 조목조목 탐구해보고 싶은 논문.
- 학생들, 수련의들이 이런생체역학의 기초과학 탐구를 해주면 얼마나 좋을까?
- 언젠가 그날이 오기를 기대하며
- 이 글을 보는 학생, 수련의들께 고합니다. 학부때, 수련의때 이런 논문을 한번 탐구해보면 얼마나 좋을까요?
ABSTRACT
Analysis of the mechanical and neural regulatory mechanisms of the flexion-relaxation phenomenon (FRP), observed in deep trunk flexion, was performed since it is believed these mechanisms provide insight into the causes of low back injury and pain. Three methods were used to analyze the behavior of the lumbar tissues during trunk flexion-extension exercises:
1) active continuous cyclic movement - 능동적이고 연속적인 반복 움직임
2) acute cyclic movement at different orientations - 각기 다른 방향으로 격렬한 반복 욱직임
3) passive continuous cyclic movement. - 수동적이고 연속적인 반복 움직임
All activities were performed at a rate of 0.1 Hz (6cycles·min-1) while monitoring the surface electromyogram (EMG) of the lumbar paraspinal muscles. Abdominal, hamstring, and quadriceps muscle activities were also monitored during acute cyclic movement.
Trunk inclination and lumbar flexion angles were time synchronized with the recorded EMG signals. Increases in the myoelectric silent period with respect to inclination and flexion angles were apparent over time (p < 0.001) during the active continuous cyclic activity.
Muscular fatigue and constant gravitational loading of the system were thought to influence the observations. Acute cyclic movements of trunk flexion-extension were performed in standing and supine positions. In standing, abdominal EMG activity increased when silent periods were present in lumbar paraspinal and hamstring muscles.
Performance of flexion-extension from the supine position resulted in sustained silence of the paraspianl muscles once gravitational load was presented as the trunk flexed beyond vertical into deep flexion. EMG activity within the paraspinal muscles increased while extension was executed. During passive continuous cyclic movement the trunk motion was controlled by an external mechanical system to isolate the movement from fatigue.
A significant decrease in the torque supplied by the posterior passive tissues was observed. EMG amplitudes remained relatively low during the passive session. A significant increase in the EMG amplitude and frequency was observed during
active flexion movements performed after the passive session. Evidence suggests the primary control mechanism of the FRP to be mechanical in origin for acute loading. Decrease stability of the spine may occur with prolonged repetitive trunk flexion-extension. The increased duration of the FRP during continuous cyclic flexion-extension suggests neural mechanisms may supersede mechanical mechanisms during repetitive lifting activities.
Example of flexion-relaxation phenomenon
Figure 1.2. Schematic of the general neural pathways from afferent receptors in active and passive tissues to the central nervous system (CNS).
Figure 2.1. A. Typical recording of EMG activity and its linear envelope during cyclic flexionextension.
Figure 2.2. Depiction of a typical subject’s EMG pattern over time
Figure 3.1. Exemplar data of EMG and flexion /inclination angles during standing
Figure 3.2. EMG activities during standing as a percentage of one trunk flexion-extension cycle
Figure 3.3. Exemplar lumbar paraspinal EMG pattern during supine trunk flexion-extension performance
Figure 3.4. A. EMG activities during supine condition as a percentage of one trunk flexionextension cycle.
Figure 3.5. Comparison of lumbar paraspinal (LP) activities between standing (LP ST) and supine (LP SU) conditions
Figure 4.1. Example of the procedures used to secure subjects during the passive trunk flexionextension session.
Figure 4.2. The stepwise procedures followed in testing during active and passive trunk flexionextension sessions
Figure A.2. Flow chart of the mechanisms hypothesized to influence the flexion-relaxation phenomenon (FRP)
Figure A.3. Stress-strain curve indicating the mechanical response of a viscoelastic tissue to loading.
Figure A.5. Hysteresis curve indicating the mechanical response of a viscoelastic tissue to loading and release of tension to a constant length over time